Pop-up irrigation sprinklers are typically buried in the ground and include a stationary housing and a riser assembly mounted within the housing and that shifts up and down in the housing. During an irrigation cycle, the riser assembly is propelled through an open upper end of the housing and projects above ground level, or “pops up,” to distribute water to surrounding terrain. More specifically, pressurized water is supplied to the sprinkler through a water supply line attached to an inlet of the housing. The pressurized water causes the riser assembly to travel upwards against the bias of a spring to the elevated spraying position above the sprinkler housing to distribute water to surrounding terrain through one or more spray nozzles. When the irrigation cycle is completed, the pressurized water supply is shut off and the riser is spring-retracted back into the sprinkler housing so that the housing and riser assembly are again at and below ground level.
The riser assembly commonly includes a sprinkler head mounted at the upper end of a stem. The sprinkler head has one or more outlets or spray nozzles and may or may not be rotatable on the stem. Rotary type sprinklers have a sprinkler head that rotates on the stem, commonly referred to as a turret. The head rotates through an adjustable arcuate water distribution pattern called a spray arc. These rotary sprinklers may include a water-driven motor to transfer energy of the incoming water into a source of power to rotate the turret. One common mechanism uses a water-driven turbine and a gear reduction system to convert the high speed rotation of the turbine into relatively low speed turret rotation.
During normal operation, the turret rotates to distribute water outwardly over surrounding terrain within the spray arc which is set by setting the end limits of rotation of the turret relative to the stem. Rotary sprinklers commonly employ an arc adjustment mechanism, where one edge of the spray arc (the start angle, for example) is fixed relative to the stem that the turret sits upon and the other edge (the end angle, for example) of the spray arc is adjustable to set the arcuate length or included angle of the spray arc.
For known sprinklers with rotatable turrets, the stem does not rotate relative to the housing during operation, that is while the turret is rotating on the stem, so that the angular direction of the spray arc can be fixed to spray over a desired area around the sprinkler. Thus, the bottom of the stem typically has a ring of outwardly-extending teeth that engage ribs extending longitudinally along an inner surface of the housing to restrict rotation of the stem relative to the housing. With this configuration, in order to change the fixed edge of the spray arc, the sprinkler must be disassembled. More specifically, for example, the stem and turret are removed from the sprinkler housing, rotated to point the outlet or other mark on the turret that defines the fixed edge of the spray arc in a desired direction, and then placed back into the housing. Other non-rotating sprinklers without rotating turrets also require the same disassembly where the outlet on the sprinkler must be pointed in a desired direction before the stem is placed back into the housing.
Also, if the user or a vandal rotates the stem in the housing, the ring, gear teeth, and/or ribs on the housing can break, leaving the stem to rotate freely. When this occurs, the outlet may shift to a different rotational position every time pressurized water pops up the stem for watering, resulting in watering undesired areas, while missing the desired area. For rotary sprinklers, the rotation of the turret also can cause undesired rotation of the free, broken stem during operation that rotates the entire spray arc set for the sprinkler so that the sprinkler is not watering the desired area.
At least for non-rotary sprinklers that receive relatively low water pressure, one attempt at a solution is provided by securing a separate ratchet ring near the bottom of the stem. The ring has outwardly extending protrusions to engage the ribs of the housing so that the ring does not rotate. The ring also has inwardly extending teeth to mesh with teeth on the stem. So configured, applying a very large rotational force on the stem will rotate the stem relative to the housing without breaking the stem, housing or ratchet ring. Thus, the ring restricts rotation of the stem during operation of the sprinkler but permits the stem to rotate to set the position of the outlet or to prevent vandals from damaging the sprinkler.
Even with the ring, however, it is still difficult to rotate the stem because the known ring configuration requires the application of a relatively large rotational force on the stem to overcome the strong forces acting on the stem. This occurs because the teeth on the ring must shift or flex out of engagement with teeth on the stem in order to rotate the stem. Thus, the ring may shift or flex upward or downward off of the stem teeth or shift radially outward from the stem teeth to provide clearance for the stem to rotate. However, the ring and its teeth are sandwiched between an end of the spring and a ledge on the bottom end of the stem. The ring is typically in this position so that the ring can remain with the lower end of the stem while the stem moves up and down due to the biasing force from the spring and/or water pressure. This results in both the biasing force of the spring (from above the ring) and the forces from the water pressure (from the ledge below the ring) applying pressure against the ring making it extremely difficult for the ring to shift or flex away from the teeth on the stem. Additionally, the spring may also bind radially against the stem further increasing the rotational force needed to rotate the stem. It becomes practically impossible to apply such a strong rotational force to the stem when a person has difficulty grasping the stem due to its small diameter. The rotational force that is required is so strong that it can break the teeth on the stem or the ring. For these reasons, this configuration also would not work on rotary sprinklers that typically have higher water pressures than the non-rotary sprinklers.
Accordingly, there has been a need for an improved sprinkler with a stem that does not rotate during normal operation but will otherwise rotate easily when desired to control the watering range.